The invention relates to a cross-country ski primarily designed for the skating technique.
It is an object of the invention to enable the skier, while running, to utilize for a longer time the kinetic energy arising from the running speed of the skier or from the impulsion energy introduced by the skier than has been possible so far with conventional skis, by a special configuration of the lateral shape or waisting of the ski.
In the skating technique, it is differentiated between two phases:
Axe2x80x94the impulsion phase
Bxe2x80x94the sliding phase.
With the skating ski, impulsion is performed by
a setting the edge of the ski SK via the edge of the running surface by a canting angle beta of between preferably 5 and 45xc2x0 relative to the snow surface SCH, as is schematically illustrated in FIG. 1, and simultaneous
b transverse positioning of the ski according to FIG. 2 at a certain excursion angle alpha, e.g. between 10 and 80xc2x0, depending on the inclination of the piste relative to the running direction, and
c by introducing an impulsion impulse (depending on the running technique and the body weight of the skier).
For the sliding phase it is suitable if the sliding direction of the ski coincides with the running direction of the skier, as schematically illustrated in FIG. 3.
Arrow A indicates the running direction in FIGS. 2 and 3.
For an optimum utilization of the energy, it is suitable if the sliding phase, i.e. The phase in which the ski follows the running direction, is as long as possible, and the impulsion phase, i.e. that phase in which the ski must be set on edge and positioned transversely, can be kept as short as possible, cf. FIG. 4. There, lines GL and GR indicate the respective sliding phase of the left and right ski, respectively, and the respective subsequent curve AL and AR, respectively, indicate the impulsion phase of the left and right ski, respectively.
To enable the above-described and illustrated sequence of movement, a ski having different geometries of lateral shape would be required.
For a straight-line movement (sliding phase) or running along a straight line, a ski having straightline or concave lateral shape according to FIGS. 5 and 6, respectively, would be required.
For an outward movement of the ski (impulsion phase), convex lateral shapes according to FIG. 7 would be required.
The known ski either has a parallel waisting or a concave waisting, in which the ends of the ski and the tips of the ski are wider than the middle part of the ski. Moreover, in particular for the skating technique, skis are known which have a convex waisting in which the ski has a larger width in its middle part than in its front and rear regions. Finally, skis are known which have a convex or parallel waisting in a certain region and are arrow-shaped towards their tips. Skis having a concave waisting have properties causing the ski, when canted, i.e. when its edge is set, to follow its concave lateral shape, i.e. if this ski, e.g., is fastened to the right foot during a skating step, it will not pull outwards in relation to the running direction, but inwards. Skis having parallel lateral shapes behave relatively neutral, yet they substantially facilitate an outward movement as compared to a ski having a concave waisting. Skis having a convex lateral shape automatically favor an outward curve, in relation to the running direction.
When considering the skating technique on an ascending ground, for attaining an ascending effect, it will be desirable for the ski to pull outwardly from the running direction so as to obtain a certain transverse positioning in relation to the running direction so that the skier can push off on the outer ski and will be able to change into the other step. Convex or parallel lateral shapes are better for this technique than concave lateral shapes which have an opposite effect. The disadvantage of convex lateral shapes consists in that the ski, according to its waisting, will automatically pull into the curve as soon as it is set on edge. FIG. 8 serves to explain this behavior of the ski having a convex lateral shape, and in that Figure arrow A indicates the skiing direction. If the skier wants to pass the distance from X to Y with a conventional ski having convex lateral shape, the ski will automatically pull along its waisting into a curve designated by a as far as to an angle which will depend on the ascent of the track insofar as the higher the ascent of the track, the more the excursion from the skiing direction must be, in order to be able to effect an impulsion. The flatter the track, the less the excursion. With the known ski, the skier will have to break off his still remaining speed at the end of this excursion in disadvantageous manner so as not to drift too far away from the longitudinal direction. After the distance S from the starting point X onwards has been passed, the skier will change his step to his second foot which passes the distance S1 in analogous manner along curve a1.
From AT 369 273 a ski, preferably an Alpine ski, has been known which in its middle region does have a convex portion and, following thereupon, a concave portion. This cut-out of the lateral shape is to solve the problem of improving the behavior of the Alpine ski on particularly slippery, steep pistes.
It is the object of the invention to stabilize the longitudinal movement of the ski by a special design of its lateral shape, or of its waisting, respectively, so that the ski will not pull as much outwardly during its sliding phase and so that the speed still prevailing need not be stopped but much rather the kinetic energy will be utilized more efficiently and by an intended pressure increase and thus change of the pressure distribution on the area underneath the ski and the concentration of the weight on the middle region of the ski at the end of the sliding phase, the ski will be brought into its impulsion phase more rapidly, whereby the skier with an equal amount of impulsion energy introduced can pass through a flatter curve b, or b1, respectively, and thus can cover a distance W, or W1, respectively, which is longer than the distance S, or S1, respectively, covered by a conventional ski.
According to the invention, this object is achieved by having a middle region, of at least one of the two side faces of at least one ski of a pair of skis, designed to be convex or parallel, preferably to the central axis of the ski or in the sliding direction perpendicular to the track. The front and/or rear region of at least one side face of at least one ski of a pair of skis is designed to be concave so that the skier can push himself off on the outer ski and can alternate into the other step.
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.